you can directly use a pic pin as open collector, when configuring output=20 data to 'low' and manipulating output direction. tino =D6mer Yalhi Gesendet von: pic microcontroller discussion list 12.06.03 11:19 Bitte antworten an pic microcontroller discussion list =20 An: PICLIST@MITVMA.MIT.EDU Kopie:=20 Thema: [EE]: Transistor / Optocoupler I would like to give an open drain output from a circuit (RA4 not=20 available).=20 The circuit works with 3V or 3.6V which transistor do I choose and what=20 resistors should I use (or how do I calculate which resistor to use given=20 the 3V input voltage) I probably can use BD138 but I don't know how to=20 connect it to my circuit and the resistor values. any help is appricated. oyalhi@teksan.com.tr -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics